Improving particulate carbon loss estimates in eroding peatlands through the use of terrestrial laser scanning

Blanket bogs act as the largest terrestrial store of carbon within the UK. Unfortunately many are degraded with exacerbated erosion being common. Although considerable efforts have been made to quantify carbon fluxes across blanket bogs, less attention has focussed on quantifying losses associated with erosion. Traditional approaches to measuring erosion have relied on erosion pins and sediment traps. However, both methods suffer from several problems and are unable to provide data over large areas. Terrestrial laser scanning has been used widely in geomorphology to create detailed 3D topographic maps in a range of environments. A pilot study was carried out over winter 2010–2011 to test the applicability of terrestrial laser scanning to measure erosion across a blanket bog within the North Pennines, UK. The technique was found to be superior to traditional methods providing high resolution spatial data on surface elevation change. A net increase in the peat surface height of 2.5 mm was calculated from the terrestrial laser scans between October 2010 and March 2011. This compares with a net surface lowering of 38 mm measured using pins. These results suggest that previous erosion data from peatland sites based on pin measurements ought to be treated with caution. However, several improvements are required to the laser scanning technique before it is fully implemented in peatland environments including the development of a filter to remove vegetation from the scan results, and taking account of ‘mire-breathing’ which can cause surface level rise and fall in peatlands. It is clear that once these factors are dealt with, regular repeated ground based laser scanning will vastly improve our understanding of the role of processes that affect the surface elevation of peatlands including the relative roles of storm events and long-term seasonal cycles, and ‘roughening’ of the peat surface as a result of needle-ice formation, desiccation and wind-scouring.